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Article
Physics, Multidisciplinary
M. Koussour et al.
Summary: In this study, the accelerated expansion of the Universe is investigated in the framework of f(Q) gravity theory, where the non-metricity scalar Q describes the gravitational interaction. A new parametrization of the Hubble parameter is proposed and applied to the Friedmann equations in the FLRW Universe. The model parameters are estimated using combined datasets and the Markov Chain Monte Carlo method. The results indicate a transition from deceleration to acceleration phase of the Universe, with support for the present accelerating Universe and behavior resembling the quintessence model.
FORTSCHRITTE DER PHYSIK-PROGRESS OF PHYSICS
(2023)
Article
Physics, Particles & Fields
M. Koussour et al.
Summary: Based on the FLRW geometry, the f(Q) gravity theory is used to address the cosmic acceleration and dark energy issues. A power law f(Q) model is applied, and the energy density and pressure of the cosmic model are determined using constant sound speed parameterizations. The field equations are derived, and the model's behavior is examined using observational data sets.
Article
Astronomy & Astrophysics
Christian Bohmer et al.
Summary: Modified gravity theories describe homogeneous and isotropic cosmological models through field equations. These equations can be transformed into autonomous differential equation systems due to their dependence on a well-chosen time variable. This allows for a reliable study of the equations using a dynamical systems approach. Through a model-independent set of variables, all f(Q) modified gravity models can be analyzed. The drawback is a more complicated constraint equation, but it reduces the dimensions of the dynamical system compared to other methods. We focus on the power-exponential model and generalize its fluid content.
Article
Physics, Multidisciplinary
Tee-How Loo et al.
Summary: The f(Q, T) theory of gravity, which incorporates the trace T of the energy-momentum tensor and the non-metricity scalar Q, has been well-studied in the cosmological application. However, considering the anisotropy of our Universe since the Planck era, it is necessary to investigate this theory in a model with small anisotropy for a complete understanding of the Universe's evolution. By using a locally rotationally symmetric (LRS) Bianchi-I spacetime and deriving the motion equations, we analyzed the model candidate f(Q, T) = & alpha;Qn+1 + & beta;T and constrained the parameter n using statistical Markov chain Monte Carlo (MCMC) method with the Bayesian approach and two independent observational datasets, namely the Hubble datasets and Type Ia supernovae (SNe Ia) datasets.
Article
Astronomy & Astrophysics
Andronikos Paliathanasis
Summary: We study the evolution of physical variables in f(Q)-gravity for two families of symmetric and flat connections in a spatially flat Friedmann-Lemaitre-Robertson-Walker geometry where the equation of motion for the nonmetricity scalar is not trivially identity. From the analysis of dynamics, we found that the de Sitter universe is always an attractor, while the cosmological models admit scaling solutions that can describe the early acceleration phase, matter epoch, and radiation epoch of our universe.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Astronomy & Astrophysics
S. A. Narawade et al.
Summary: This paper investigates the dynamical aspect of the accelerating cosmological model in the framework of modified symmetric teleparallel gravity, the f(Q) gravity. The dynamical parameters for two well-known forms of f(Q) are derived, namely the log-square-root form and the exponential form. The equation of state parameter for dark energy in the f(Q) gravity is found to be a dynamical quantity. The stability behavior and cosmological behavior of the models are analyzed using dynamical system analysis, and the evolutionary behavior of density parameters for different phases is also shown.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Physics, Particles & Fields
A. S. Agrawal et al.
Summary: In this paper, we have presented the matter bounce scenario of the Universe within an extended symmetric teleparallel gravity, known as the f (Q) gravity. By incorporating the bouncing scenario and loop quantum cosmology, we have determined the form of the function f (Q) within the Friedmann-Lemaitre-Robertson Walker space-time. Considering a background cosmology dominated by dust fluid, we have expressed the e-folding parameter that includes the nonmetricity term. Due to the invalidity of the slow roll criterion in the bouncing context, we have utilized a conformal equivalence between f (Q) and scalar-tensor model to apply the bottom-up reconstruction technique. The dynamics of the model have been examined through phase space analysis, yielding both stable and unstable nodes. Furthermore, stability analysis has been performed on the first-order scalar perturbation of the Hubble parameter and matter energy density to confirm the stability of the model.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Astronomy & Astrophysics
Antonio Najera et al.
Summary: We developed the cosmological linear theory of perturbations for f(Q, T) gravity and analyzed the coupling between Q and T as well as the properties related to scalar and tensor perturbations. Our analysis suggests that f(Q, T) gravity could serve as a good alternative to dark matter in certain cases, and we provided a method for further studying this theory.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
S. A. Narawade et al.
Summary: Two accelerating cosmological models based on symmetric teleparallel f(Q) gravity are introduced, with Q representing non-metricity. These models are constructed with different functional forms of f(Q) and a dynamically changing deceleration parameter. The dark energy in f(Q) gravity exhibits a dynamical equation of state parameter and crosses the phantom divide line.
PHYSICS OF THE DARK UNIVERSE
(2022)
Article
Astronomy & Astrophysics
Andreas Lymperis
Summary: By investigating the features of a non-metricity scalar Q function, the cosmological implications of f(Q) gravity are explored, and analytical expressions for the dark energy density, equation-of-state, and deceleration parameters are obtained. The study reveals that even in the absence of a cosmological constant, the universe follows the usual thermal history with matter and dark energy eras, and the dark energy equation-of-state parameter remains in the phantom regime. Additionally, the scenario shows excellent agreement with observational data from Supernovae type Ia. Furthermore, it is demonstrated that f(Q) gravity can effectively mimic the behavior of a cosmological constant.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Aaron Glanville et al.
Summary: With recent evidence for a possible 'curvature tension' among early and late universe cosmological probes, Effective Field Theories of Large Scale Structure (EFTofLSS) have emerged as a promising new framework to generate constraints on Ok that are independent of both CMB measurements, and some of the assumptions of flatness that enter into other large-scale structure analyses. In this work we use EFI'olLSS to simultaneously constrain measurements from the 6dFGS, BOSS, and eBOSS catalogues, representing the most expansive full-shape investigation of curvature to date. Using the Bayesian evidence ratio our full-shape data assigns betting odds of 2:1 in favour of curvature, indicating present measurements remain broadly compatible with both flat and curved cosmological models. When our full-shape sample is combined with Planck 2018 CMB measurements, we break the geometric degeneracy and recover a joint fit on Omega(k) of -0.0037(-)(0.0026)(+0.0025) Using the suspiciousness statistic we find evidence for a moderate tension between Planck 2018 and our suite of full-shape measurements, at a significance of 1.86(-0.11)(+0.13)sigma (p similar to 0.06 +/- 0.02). These results demonstrate the usefulness of full-shape clustering measurements as a CMB independent probe of curvature in the ongoing curvature tension debate.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Physics, Particles & Fields
Dehao Zhao
Summary: In Symmetric Teleparallel General Relativity, gravity is attributed to non-metricity. However, the coordinate system selected based on symmetry may conflict with the choice of coincident gauge. To overcome this problem, we formulate the f(Q) theory in a covariant way, allowing us to find suitable non-vanishing affine connection.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Astronomy & Astrophysics
Suhail Dhawan et al.
Summary: This study proposes a non-parametric method to infer the spatial curvature parameter Omega(K) from late-Universe probes, obtaining constraints that are free from parametric model assumptions and insensitive to overall calibration. Applying this method to future surveys, it is forecasted that Omega(K) can be constrained at the O(10-2) level.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
S. H. Shekh
Summary: This study dedicates to the dynamical investigation of models of holographic dark energy using FLRW cosmological model in the context of modified gravity, where the Lagrangian is the arbitrary function of the trace of the non-metricity tensor Q in f(Q) gravity. It discusses the features of the derived cosmological model in terms of the relation between cosmic time and redshift, as well as the evolution trajectories of the equation of state parameter and stability parameters in the evolving universe. The classification of the field equations towards f(Q) = Q + mQ(n) reveals that the model is purely accelerating corresponds to 0 <= q <= -1.
PHYSICS OF THE DARK UNIVERSE
(2021)
Article
Astronomy & Astrophysics
Sunny Vagnozzi et al.
Summary: The debate over the concordance of the ACDM cosmological model in light of current observations remains ongoing. However, utilizing measurements from datasets such as the Baryon Oscillation Spectroscopic Survey can help break the geometrical degeneracy, providing new perspectives on a flat Universe while also revealing tension between Planck and P(k) data under the assumption of a curved Universe.
PHYSICS OF THE DARK UNIVERSE
(2021)
Article
Astronomy & Astrophysics
Manuel Hohmann
Summary: Symmetric teleparallel gravity theories focus on the nonmetricity of a flat, symmetric affine connection as the source of gravitational interaction, with recent studies exploring their cosmological implications. However, assumptions made in these studies, such as flat FLRW metric and vanishing connection coefficients, may not always be compatible. By constructing a general symmetric teleparallel geometry without coordinate constraints, it is found that coordinate systems do not always agree, limiting the class of achievable geometries. This study highlights the additional scalar quantity contributed by the symmetric teleparallel connection to cosmological dynamics, decoupling only under specific conditions.
Article
Astronomy & Astrophysics
Luis Atayde et al.
Summary: Observational constraints were studied on nonmetricity f(Q)-gravity, reproducing an exact Lambda CDM background expansion history while modifying the evolution of linear perturbations. By utilizing various measurements, it was found that the model is preferred over Lambda CDM in certain statistical aspects, primarily due to a better fit to the low-l tail of CMB temperature anisotropies.
Article
Astronomy & Astrophysics
Wompherdeiki Khyllep et al.
Summary: The study investigates one of Einstein's alternative formulations based on nonmetricity scalar Q generalized as f(Q) theory, focusing on the power-law form of f(Q) gravity. The analysis reveals that the geometric component of the theory determines the late-time acceleration of the Universe, and the model deviates from ΛCDM even for |n| < 1 at the perturbation level. The integrability of the model is examined using singularity analysis, finding conditions under which field equations pass the Painleve test and possess the Painleve property.
Article
Astronomy & Astrophysics
Sunny Vagnozzi et al.
Summary: Recent studies have discussed the question of whether the universe is spatially closed by combining Planck data with external data sets, ultimately concluding that the universe is spatially flat. By utilizing cosmic chronometers data to break the geometrical degeneracy, the study provides a stable estimate of the spatial curvature of the universe.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Eleonora Di Valentino et al.
Article
Astronomy & Astrophysics
Jose Beltran Jimenez et al.
Article
Astronomy & Astrophysics
Jose Beltran Jimenez et al.
Article
Astronomy & Astrophysics
Jose Beltran Jimenez et al.
Article
Astronomy & Astrophysics
Andronikos Paliathanasis et al.
Article
Physics, Particles & Fields
Antonio De Felice et al.
Living Reviews in Relativity
(2013)
Article
Physics, Nuclear
Genly Leon
INTERNATIONAL JOURNAL OF MODERN PHYSICS E-NUCLEAR PHYSICS
(2011)
Article
Astronomy & Astrophysics
Andronikos Paliathanasis et al.
Review
Astronomy & Astrophysics
Edmund J. Copeland et al.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2006)
Article
Astronomy & Astrophysics
C Rubano et al.
